Today, known sensor-bearing units are not fully adapted to be implemented in oil lubricated environments, such an apparatus of the electric motor type.
The same or a different lubricant can be used for the bearing and the apparatus. The bearing can be provided with sealing members on its axial sides to avoid oil leak out of the bearing or entry into the bearing. As an alternative, the bearing can be fully open to allow oil flow between its rotating and non-rotating rings.
The detection device usually comprises a sensor fixed to the non-rotating ring and a target fixed to the rotating ring of the bearing. The detection device can also be provided with sealing members or a labyrinth to avoid or reduce oil entry between the sensor and the target. Indeed, efficiency of known detection device may be reduced in operation due to the oil contamination. However, these devices have a complex structure.
EP-A-1 557 676 describes a sensor-bearing unit, which is not adapted for a proper oil flow. According to a first embodiment, this unit comprises a target fixed to the inner ring and a sensor fixed to the outer ring of the bearing. The sensor comprises a sensor cover forming a retainer, where oil can stagnate and particles can settle, so that the sensor operation can be disturbed. Moreover, the sensor cover extends towards central axis beyond the target and forms a shield opposed to oil flow through the unit. In other words, this unit is not adapted for implementation in oil lubricated environments.